DIRECTIONAL CHARACTERISTIC OF RESISTIVITY CHANGES IN ROCK OF ORIGINAL RESISTIVITY ANISOTROPY
原始电阻率各向异性岩石电阻率变化的方向性

Multiple electrodes are arranged on the surfaces of samples, which include three kinds of resistivity of anisotropic samples not formed by ingredient of rock (The original resistivity anisotropy of the samples is due to the integrity of samples be damaged in the process of sampling and processing) and a kind of samples formed by ingredient of rock. The samples are fully saturated with water. The multiple electrodes are combined form arrays of resistivity changing anisotropy in different direction and spacing. The experiments of dynamic rock resistivity change are done with uniaxially compression, low confining pressure and shear. The variations of resistivity during the whole loading process are observed. The experimental results are the following: The samples of original resistivity anisotropy are essentially accordant with the samples of original resistivity isotropy in resistivity changing anisotropy. Namely, for the measuring-points located at cracks or rupture bands, the results of resistivity changing anisotropy are good, the four directions deduced from four kinds of combinatorial equation sets of resistivity are essentially identical with each other and approximately coincide with the orientation of cracks or main rupture bands; for the measuring-points without cracks or rupture bands passing through, the four directions calculated by different combinatorial arrays of resistivity are inconsistent with each other, or the direction can not be determined, especially in the cases when the crack plane is parallel to the measuring-surface.